Information AboutGssp |
| CATEGORIES ABOUT GLOBAL BOUNDARY STRATOTYPE SECTION AND POINT | |
| geologic time scale | |
| stratigraphy | |
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An ideal GSSP would
No GSSP is ideal. AGREED-UPON GSSPS The Precambrian - Cambrian boundary GSSP at Fortune Head , Newfoundland is a typical GSSP. It is accessible by paved road and is set aside as a Nature Preserve . A continuous section is available from beds that are clearly Precambrian into beds that are clearly Cambrian. The boundary is set at the first appearance of a complex trace fossil '' Trichophycus Pedum '' that is found worldwide. The Fortune Head GSSP is unlikely to be washed away or built over. ''Trichophycus pedum'' is less than ideal as a marker fossil as it is not found in every Cambrian sequence, and it is not assured that it is found at the same level in every exposure. But no other fossil is known that would be preferable. There is no Radiometrically Datable bed at the boundary at Fortune Head, but there is one slightly above the boundary in similar beds not very far away. Once a GSSP boundary has been agreed upon, a "golden spike" is driven into the geologic section to mark the precise boundary for future geologists (though in practice the "spike" need neither be golden nor an actual spike). The first stratigraphic boundary was defined in 1977 by identifying the Silurian - Devonian boundary with a bronze plaque at a locality called Klonk, northeast of the village of Suchomastyin in the Czech Republic . GSSPs are also sometimes referred to as Golden Spikes. GSSAS Because defining a GSSP depends on finding well-preserved geologic sections and identifying key events, this task becomes more difficult as one goes farther back in time. Before 630 million years ago, boundaries on the geologic timescale are defined simply by reference to fixed dates, known as Global Standard Stratigraphic Age s. EXTERNAL LINKS REFERENCE
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